Bird abundance - point counts

Circular plot counts are used to measure relative numbers of birds over time and between sites. The duration of each count is 10 minutes. During this period, all birds heard or seen are recorded on a data sheet in one of two categories: 1) within 25 m of the observer (< 25 m) and 2) further than 25m from the observer (> 25 m). Records are further broken down into birds only heard (H on the data sheet) and birds observed (recorded as estimated distance from the sampling point in meters; see sample data sheet). Counts are begun as soon after dawn as possible and conclude before noon. Census points are at least 60 m apart within the grids. A complete list of the grid points where counts are taken is found in the data. Originally counts were conducted three times a year.